But I get an exception because unlike in c I don't see the string here ends with a null character.
Is there any other way (apart from using built functions/try catch block in case of exception) I can read all the characters of the string ?

A char array is not a string. A string is a string. And strings in C# are not null terminated. And Length is not a function, and it is O(1) to compute, not O(n). I suspect you are a C programmer; remember, C# is a different language.
–
Eric LippertJul 14 '13 at 15:02